1. Field of Invention
This invention relates to data security. Specifically, the present invention relates to systems and methods for preventing the mis-authentication of signals or data.
2. Description of the Related Art
Signal authentication systems are employed in various demanding applications including cellular telephony, wireless communications, e-commerce transactions, and GPS navigation. Such applications demand efficient and cost-effective authentication systems that impose minimal design and operational constraints on accompanying communications systems.
To facilitate signal authentication, spread spectrum communications systems are often employed. In a conventional spread spectrum system, signals are encoded and spread over a predetermined bandwidth via a pseudo random spreading sequence, also called a Pseudo-Noise (PN) sequence. A receiver often employs a copy of the spreading sequence to coherently detect, decode, and authenticate received spread spectrum signals. The de-spreading sequence used by the receiver represents an internal copy of the broadcast waveform. Unfortunately, the de-spreading sequence used by a receiver may be indistinguishable from the desired signal and thus may be detected by, or may interfere with, other receivers also searching for the original signals.
Signal authentication systems are particularly important in applications where jamming or spoofing is problematic. To prevent misuse of the de-spreading sequence, anti-tamper devices may be employed. However, conventional anti-tamper devices are often readily circumvented. Furthermore, enclosing all signal-processing components and activities within a tamper-resistant container places undesirable design constraints on associated receiver and transmitter systems. The design constraints may increase system size, complexity, and cost. Furthermore, conventional tamper-resistant containers often complicate or inhibit system upgrades.
GPS systems transmit navigation signals using a spread-spectrum modulation scheme. GPS signals are encoded with a PN sequence. The encoded (spread) signals are transmitted from satellites to receivers, such as GPS navigation receivers. The GPS receivers can time signals received from different satellites with known positions to determine the current position of the receiver. Ideally, only receivers that can generate the PN sequence corresponding to the transmitted signal can decode and use the signal broadcast from the satellite.
To jam a GPS satellite signal, a GPS jammer may broadcast false. GPS signals. To overcome GPS jamming, various well-known signal authentication methods may be employed to distinguish between jamming signals and authentic signals. Unfortunately, conventional authentication systems may require lengthy GPS signal tracking. The significant signal tracking time required for authentication may delay valid GPS navigation signal acquisition and use.
Hence, a need exists in the art for an efficient system and method for enabling robust signal authentication while facilitating system upgrades. There exists a further need for a communications system incorporating an efficient authentication system that inhibits jamming and that may reduce communications system noise.